1. Technical Field
The present invention relates to an apparatus and method for transmitting audio and video signals over extended lengths of unshielded twisted pair cable.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 & 1.98
The prior art includes various transmission and receiving units for audio and visual signals. The combination of the unique systems of this invention to transport audio and visual signals over unshielded twisted pair cable is not believed to have been disclosed in the prior art.
More specifically, the prior art includes U.S. Pat. No. 7,064,190 to Gershfeld and Pat. Pub. 2003/0201802 to Young. However, both Gershfeld and Young distincty teach against transmitting synchronization signals wherein the first and second synchronization signals act as a differential signal across the common mode of the first and second pairs of the four twisted wire pairs and the common mode of said third and fourth pair of the four twisted pairs, respectfully. For example, Young teaches about a third common mode differential signal, that such a signal is “slower in speed”, but still “may be useful for a number of things”. Although Young lists specific possible uses for such a differential signal, including handshaking control, flow control, status, and functions not requiring a high-speed data rate; (real time) video synchronization is notably absent from this list.
Furthermore, Young teaches that the common mode differential signal (across two other differential data signals) can be used to transmit data when the “three data signals . . . do not have to be synchronized with each other”. In stark contrast, the instant invention requires that both the first and second synchronization signals are tightly synchronized with the associated video information in order to produce an acceptable display.
This need to maintain close synchronization between the synchronization signals (i.e., horizontal and vertical sync) is inherently taught in Gershfeld where the horizontal sync is superimposed onto the green video signal and the vertical sync is superimposed onto the red video signal. On the other hand, the instant invention completely separates the synchronization signals from the associated video content.
Applicants' inventive video transport system comprises a transmit unit adapted to transmit first and second synchronization signals across the common modes of four twisted wire pairs. Synchronization signals by their nature are time sensitive signals. It would not be intuitive to one skilled in the art to transmit such signals on time skewed transmission paths, such as the common mode of twisted pairs.
The unique systems of applicants' invention to transport audio and visual signals over unshielded twisted pair cable is not believed patentable over the known prior art. Furthermore, the invention is not rendered obvious by any combination of multiple references from analogous fields.